1. Field of the Invention
The present invention relates to a method for manufacturing a surface-coated cutting insert which is mounted to various insert-removable machine tools and is used for metal cutting.
This application claims priority from Japanese Patent Application No. 2005-349651 filed on Dec. 2, 2005, the content of which is incorporated herein by reference.
2. Background Art
A cutting insert has an insert body with a hard material, such as tungsten carbide-based cemented carbide, titanium carbonitride-based cermet or ceramics, and the like as the substrate (e.g., in the shape of a polygonal plate), in which a cutting edge is formed at the intersecting edge line region of its rake face and flank face, and the cutting insert is mounted to insert-removable machine tools and has been widely used for metal cutting. As for such cutting inserts, surface-coated cutting inserts coated with a coating layer which is formed into a single layer or two or more layers with carbide, nitride, oxide, boride of one selected from Groups IVa, Va, VIa metals of the periodic table of elements, Al and Si, or their composite compounds on the surface of the insert body have also been proposed for mainly improving their wear resistance.
As such surface-coated cutting inserts, an insert in which a portion of the coating layer is mechanically removed or the surface of the coating layer is smoothened has also been proposed. For example, it has been disclosed in Patent Document 1 that a TiCxNyOz layer formed on an α-Al2O3 layer is mechanically removed from only the cutting edge line or from both of the rake face and the cutting edge line, and the TiCxNyOz layer remains on the flank face. It has also been disclosed that Al2O3 having strong resistance to diffusion-type crater wear or welding (smearing) is used for the outermost layer of the rake face and the cutting edge, and a TiCxNyOz having strong resistance to flank wear is used for the outermost layer of the flank face in place of Al2O3 which is worn out in a relatively early stage; thereby, excellent wear resistance is simultaneously displayed at the rake face and the flank face. Moreover, brushing, polishing, or dry and wet blasting treatment are given as forms of mechanical removal.
In Patent Document 2, it has been shown that a wear-indicating layer is provided on the flank face so as to enable simply detecting whether the cutting edge is unused or used. It also shows a method in which an Al2O3 layer is desirably coated as an wear reducing coating and then a TiN layer is coated as an outermost layer, subsequently the TiN layer which is a wear-indicating layer is mechanically removed by a brush or a sandblast from the rake face and the cutting edge.
In such mechanical removal of the coating layers described in Patent Documents 1 and 2, the brushing using a brush or the polishing treatment is carried out wherein the surface of a cutting insert is polished with a nylon brush containing, for example, abrasive grains, a brush of animal bristle added with diamond paste or an elastic grindstone, and the like
However, such treatment is high working energy treatment that is also applied to a honing treatment and a lapping treatment of cutting edges in a normal cutting insert. Moreover, it is feared that because the working energy strongly acts on the above-described intersecting edge line region where the cutting edge especially protruding from the insert body is formed, the treatment could not stop with the removal of the outermost TiCxNyOz layer or TiN layer in that intersecting edge line region and the Al2O3 layer under the layers is also ground and thinned locally. In the blasting treatment such as dry sandblast, and the like, it is also feared that the working energy still increases, consequently grinding scratches and the like are generated at the surface of the Al2O3 layer exposed by removing the outermost layer, particularly, the surface roughness is deteriorated or the reduction of toughness of the insert itself is brought about.
In the above-mentioned brushing and polishing using the brush or the elastic grindstone, the cutting insert can be treated only one side by one side. It is unavoidable to lower the treatment efficiency for a negative type cutting insert and the like in which edges are formed at both of the top face and the bottom face of a plate insert body. Even in the dry or wet blasting treatment using sandblasting, for example, if the blasting treatment is applied on condition that a cutting insert is fit into a hole formed in a jig of rigid urethane and the like or a pin provided on a jig is inserted into a mounting hole of the cutting insert so as to set the cutting insert on the jig, the treatment still can be made only one side by one side, and in addition if the jetting direction of abrasive material of the sandblast is in one direction, the whole periphery of the cutting insert is not uniformly treated, thus a cutting insert with a partially different state of cutting edge or rake face is manufactured.
The present invention was made under such a background and its purpose is to provide a method for manufacturing a surface-coated cutting insert which does not remove a coating layer more than necessary or does not deteriorate the surface roughness and is capable of making a uniform and efficient treatment when the cutting insert formed with the coating layer at the surface of the insert body is subjected to a treatment of removing a portion of the coating layer or smoothening the surface.
(Patent Document 1) Japanese Patent Application, First Publication No. H8-52603
(Patent Document 2) Japanese Patent Application, First Publication No. 2002-144108